Subacute Low Back Pain in Active Duty: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Subacute Low Back Pain in Active Duty (NCT03502187), a randomized na study. The primary outcome is Lower Back Strength-Extension.

2. Clinical Question

The trial’s overall objective, as described in the registry, was to compare three home-managed regimens for subacute low back pain: PEP, NMES core-strength training, and PCM. The specific aim was to assess whether the two regimens added to PCM were more efficacious than PCM alone across lower-back muscle strength, daily physical activity, physical function, quality of life, and symptoms associated with subacute low back pain. The listed primary outcome is narrower than that broad objective: it is lower-back strength measured during torso extension.

The outcome list also includes current pain severity, the impact of bodily pain on normal work, physical activity, mobility or function tests, and depressive symptoms. These outcomes provide additional dimensions of the condition and participants’ function, but no estimates for them are available in the registry record. The clinical question is therefore identifiable, while its answer cannot be determined from the posted results represented in this record.

3. Trial Design

This is a randomized, controlled, parallel-group trial with no masking listed in the registry. The recorded enrollment is 133. The registry names three groups: PCM, NMES, and PEP. Its summary describes the two treatment arms as supplemented by PCM, with PCM alone serving as the comparator. The registry does not report the allocation ratio, the method used to generate the random sequence, or how assignments were concealed before enrollment.

The primary outcome is lower-back strength during extension, expressed in kg-Force and summarized as a mean with standard deviation. Measurements are scheduled at 0, 3, 6, and 9 weeks. The record describes a modified strength-test system and a digital hand dynamometer. Participants make two maximal efforts, with each voluntary isometric exertion maintained for 5 seconds and separated by 30-second rest; the higher of the two trial values is accepted.

The registry lists secondary outcomes covering pain, bodily pain’s effect on normal work, physical activity, mobility or function, and depressive symptoms. The mobility and function measures include the 2-minute push-up test, the 2-minute sit-up test, and the 6-minute walk test. The record is marked completed, with a start date of 2018-04-17 and a primary completion date of 2020-05-28.

Important design details are not reported in the registry record. These include the eligibility criteria, the allocation procedure, the precise timing of each secondary outcome, adherence procedures, and the planned statistical analysis. The registry’s design labels describe the broad structure, but do not establish how repeated measurements or missing observations were to be handled.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: 5 participants completed the consent but withdrew from the study prior to being assigned to a group.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Lower Back Strength-Extension, measured over 0, 3, 6, and 9 weeks.

The primary endpoint is lower-back strength during extension, measured in kg-Force. It is intended to quantify force produced by the torso extensor muscles. The registry describes the participant standing with the lower abdomen against a padded board, with a belt around the back and under the arms. The participant pulls against the belt as forcefully as possible. Two maximal efforts are performed, and the higher value is accepted.

Strength is a direct functional measure relevant to the trial’s stated interest in lower-back muscle strength. Unlike a symptom rating, it records physical force under a standardized test procedure. It is one component of the trial’s broader aims, which also include activity, physical function, quality of life, and symptoms. The registry describes this endpoint as a continuous measure summarized by its mean and standard deviation.

Measurements are scheduled at 0, 3, 6, and 9 weeks. This creates a repeated assessment of strength over the study period, rather than a single measurement alone. However, the registry record does not specify which time point or contrast was designated for the primary treatment comparison, how measurements across time were intended to be analyzed, or whether a baseline-adjusted estimate was planned.

No group means, standard deviations, treatment-effect estimates, or confidence intervals for this endpoint are reported in the registry record. The measurement description explains what the endpoint represents, but cannot establish whether strength changed or whether groups differed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the design label establish? The registry describes the trial as randomized and parallel-group, with no masking. Randomization is a design method intended to make treatment groups comparable on average at assignment, including with respect to factors that are not measured. A parallel-group design assigns participants to a group and compares the groups’ outcomes. These general properties do not guarantee balanced groups in a particular trial, and they do not reveal the actual allocation process. The sequence-generation method, concealment procedure, and allocation ratio are not reported in the registry record.

What does a mean and standard deviation describe? The primary endpoint is continuous, with the registry specifying a mean and standard deviation. In general, a mean describes the center of a set of measurements, while a standard deviation describes their spread around that center. These are descriptive summaries; on their own, they do not show whether a difference between groups is compatible with chance or how precisely a treatment effect has been estimated. Group summaries and a comparative estimate are both needed to interpret the primary question. The record does not report those outcome values.

How should repeated assessments be understood? The strength endpoint is scheduled at 0, 3, 6, and 9 weeks. In general, repeated observations from the same participant are related rather than independent. An analysis may compare groups at a selected follow-up time, compare changes from baseline, or model the pattern across time. These approaches answer different questions and can require different assumptions. The registry record does not state the primary time point or contrast, or the statistical method for handling repeated observations. It is therefore not possible to identify the intended estimand or assess whether an analysis matched it.

Why does the analysis plan matter? A statistical analysis plan identifies which outcome contrasts are primary, how variables are represented, which participants enter each analysis, and how uncertainty is quantified. It may also state how baseline values, protocol deviations, and missing measurements are addressed. Those details are not reported in the registry record. The fact that the primary outcome is measured at multiple times makes the missing specification especially relevant: without it, a reader cannot determine which comparison would constitute the main test of the trial’s question.

What does a confidence interval contribute? In general, a confidence interval gives a range of values compatible with the data and the specified statistical procedure. It communicates precision as well as the direction and scale of an estimated effect. A narrow interval indicates greater precision than a wide interval, but the interval’s interpretation depends on the analysis and assumptions used. No confidence intervals are reported for the primary outcome in the registry record. Thus, neither the magnitude nor the precision of a primary treatment comparison can be assessed.

What role would a p-value play? In general, a p-value summarizes how surprising data at least as extreme as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it does not measure clinical importance. A p-value without an effect estimate and confidence interval is also an incomplete account of results. The record does not post p-values for the primary outcome. No claim about statistical significance can be made from the information recorded.

How should the sample-size illustrations be read? Any sample-size values associated with the record are planning illustrations based on a fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are not the trial’s observed power, and they are not evidence that the original design used those assumptions. The registry record does not report a sample-size justification or the effect size used for the trial’s design. These distinctions matter because planning calculations describe hypothetical future-study requirements under stated assumptions; they do not replace an estimate of the effect observed in a completed trial.

What can be said about distributional assumptions? For a continuous outcome, analyses often rely on assumptions about the distribution of measurements or model errors. In general, departures such as skewness or influential extreme values can affect estimates and uncertainty, particularly in small samples. Repeated-measures models may also require assumptions about how observations within a participant are related. The registry record does not report diagnostic checks, transformations, model details, or sensitivity analyses. It is not possible to determine which assumptions were evaluated or whether alternative analyses were considered.

How do the secondary outcomes affect interpretation? The trial includes several types of secondary measures, such as pain, activity, function, and depressive symptoms. When many outcomes, time points, or comparisons are examined, the chance of at least one apparently unusual result can increase. In general, multiplicity procedures or a prespecified hierarchy can help manage that issue, but their use must be assessed from the actual analysis plan and results. Neither a multiplicity strategy nor results for the secondary outcomes are reported in the registry record. No claim about adjustment or selective reporting can therefore be made.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary strength outcome measured at 0, 3, 6, and 9 weeks, as well as several secondary outcomes. Multiple outcomes and assessment times create multiple possible comparisons. In general, examining many comparisons can increase the chance of observing a result that appears notable by chance. A prespecified primary contrast, a testing hierarchy, or another multiplicity strategy can clarify how such results should be interpreted. The registry record does not report whether any such strategy was planned or used.

The record lists 9 outcome measures and 0 analyses. It does not provide outcome estimates, participant counts for each outcome assessment, or details of analysis populations. The handling of missing measurements, withdrawals, protocol deviations, or incomplete follow-up is not reported in the registry record. It also does not say whether analyses were based on all randomized participants or on a subset defined by treatment received or data availability.

These omissions limit interpretation in different ways. Without an analysis population, it is unclear which participants contribute to any eventual estimate. Without a missing-data approach, it is impossible to assess how incomplete measurements might affect estimates. Without a multiplicity plan, the role of secondary findings or comparisons across time cannot be judged. None of these gaps establishes that a particular method was or was not used; they mean the relevant details are not reported in the registry record.

Because no results are posted in the record, there is no basis to assess the balance of missing data across groups, compare analyses under alternative assumptions, or interpret any multiplicity-adjusted estimates. The clinical question remains unanswered by this record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry’s adverse-event entries list 0 serious events and 0 deaths for PCM, NMES, and PEP. The entries also list 0 other events in each group. The recorded at-risk counts are 43 for PCM, 43 for NMES, and 42 for PEP. No serious adverse-event terms are listed.

These figures should be read as the adverse-event information recorded in the registry, rather than as a complete characterization of safety. The record does not provide event definitions, monitoring procedures, reporting windows, severity details, or a narrative explaining how events were collected and classified. It also does not say whether all participants were assessed in the same way for adverse events. A recorded zero is not a substitute for information about ascertainment or follow-up.

The listed entries do not establish that no event of any kind occurred outside the recorded categories or reporting process. They describe what the registry reports for serious events, other events, and deaths. Since the record contains no outcome analyses, these entries also do not provide a comparative statistical estimate of safety between groups. They should not be interpreted as proof that the interventions are safe or that risks are identical.

12. What the Result Does, and Does Not, Mean

The registry record establishes that a randomized, parallel-group trial was conducted to compare PCM alone with two home-managed treatment approaches added to PCM. It identifies lower-back extension strength as the primary outcome and describes how that measurement was obtained. It also records a completed trial and gives the assessment schedule. These details make the intended research question and measurement approach understandable.

What the record does not establish is whether either treatment approach changed strength, whether groups differed, or how large or precise any difference was. There are no posted outcome means, standard deviations, effect estimates, confidence intervals, or p-values. The record likewise contains no analyses of the listed secondary outcomes. In the absence of those results, it is not possible to determine whether the trial’s stated objectives were met or to compare the regimens’ observed outcomes.

A completed status is an administrative registry status, not a result. Likewise, an enrollment entry does not establish that all enrolled participants contributed data to every outcome analysis. The registry does not report analysis populations or missing-data handling. The adverse-event entries report zero events in the listed categories, but do not provide enough detail to assess the completeness of safety monitoring or the scope of reporting.

General statistical interpretation distinguishes absence of evidence from evidence of no effect. When estimates and uncertainty are unavailable, neither a meaningful difference nor a lack of meaningful difference can be inferred. A later report with group-level results, analysis methods, and participant flow could address questions that this registry record leaves open. Until then, the defensible conclusion is limited to the design and outcomes the trial set out to examine, not the comparative effects of its interventions.

13. Why This Trial Matters Statistically

This trial is statistically notable for a mismatch between a clearly stated comparative question and the absence of posted outcome analyses in the registry record. The record identifies randomized assignment, three groups, a continuous primary outcome, and assessments at 0, 3, 6, and 9 weeks. These elements define the broad structure of the study, but they are not enough to evaluate the primary comparison without estimates and a description of the analysis.

Repeated measurement adds an important interpretive issue. A comparison at a particular follow-up, a comparison of change from baseline, and a comparison of outcome patterns over time can yield different answers. The registry does not identify which contrast was primary or how measurements within participants were handled. That makes it difficult to know what result would directly answer the stated question, even if summary data were available elsewhere.

The trial also includes several secondary outcomes spanning symptoms, activity, and function. Such breadth can be valuable because low back pain can be assessed in more than one way. Statistically, however, a reader needs to know which outcomes and comparisons were prespecified and how multiplicity was addressed. The registry record does not report that information or any corresponding analyses.

For biostatisticians and clinical researchers, the case illustrates why registration details, outcome definitions, analysis plans, and posted results serve different purposes. A registry record can describe the study’s intended question and methods without supplying evidence about the observed treatment effects. Clear outcome reporting, participant accounting, and uncertainty estimates are needed to connect the design to a reliable interpretation.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation of interpreting this trial from the registry record is that no outcome results or analysis estimates are posted. The primary strength measure is described, but there are no group-level means or standard deviations, treatment-effect estimates, confidence intervals, or p-values. The registry record therefore does not allow assessment of the magnitude, direction, or precision of the primary comparison.

The primary outcome is assessed at several times, but the record does not identify a primary follow-up contrast or explain how repeated measurements were analyzed. It does not report a statistical model, baseline adjustment, or assumptions used for analysis. The sequence-generation and allocation-concealment methods are also not reported, so the randomization process cannot be evaluated beyond the design label.

The record does not give detailed eligibility criteria or a full description of the enrolled population. It does not report participant flow, the number contributing to each outcome at each assessment, analysis populations, or missing-data procedures. Consequently, the implications of incomplete follow-up or exclusions cannot be examined.

Several secondary outcomes and assessment times create potential multiplicity concerns, but no testing hierarchy or adjustment approach is reported. The record also does not include a sample-size justification for the trial’s original design. Any planning illustrations based on an observed effect should not be mistaken for the trial’s original sample-size rationale or for observed power.

Safety interpretation is limited as well. The registry lists zero serious and other adverse events and zero deaths in its group entries, but does not describe how events were defined, collected, monitored, or reported. These limitations are specific to the information available in the registry record and do not establish what may be reported elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Subacute Low Back Pain in Active Duty — NCT03502187.
• Registry record last updated 2022-01-25; status last verified 2020-02.
• Results first posted 2022-01-25.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes NCT03502187, titled “Subacute Low Back Pain in Active Duty.” It is a completed, randomized, controlled, parallel-group trial with no masking listed and enrollment of 133. The recorded start date is 2018-04-17, and the primary completion date is 2020-05-28.

The three named groups are Primary Care Management (PCM), neuromuscular electrical stimulation (NMES), and the Progressive Exercise Plan (PEP). The summary describes each home-managed treatment arm as supplemented by PCM, with PCM alone as the comparator. The primary outcome is lower-back extension strength in kg-Force, measured at 0, 3, 6, and 9 weeks and summarized as a mean with standard deviation.

Secondary measures cover pain, physical activity, work impact, mobility or function, and depressive symptoms. The registry record lists zero analyses and does not post outcome estimates. Its adverse-event entries list zero serious events, zero other events, and zero deaths for the named groups. The record does not report a statistical analysis plan, missing-data methods, or detailed analysis populations.